The case for strawApril 2008

The Knowledge Transfer Network (KTN) is identifying many new products and services that could easily be adopted by the UK construction industry. David Churcher explains how straw can be turned into a highly engineered building product.

StrawJet Inc, an US-based organisation, has developed an innovative manufacturing system for automated straw bale wall construction. The new approach aims to be an alternative to resource-depleting construction methods, and suitable for application in developing countries.

Traditional straw bale construction methods involve the crushing and chopping of straws. This is a labour-intensive process which does not always lead to products with good structural properties.

StrawJet uses the whole plant stem. The straws are fed into StrawJet machines, directly from a harvester or by hand, to be bundled into cables about 50 mm in diameter. The cables can then be combined into individual construction members or into panels and wall systems.

Non-toxic binding materials can be used, such as clay, soil and paper pulp. Alternate layers are oriented at right angles to provide strength along both directions.

The compressive strength of straw when loaded parallel with the stem is impressive, and the final walling system is suitable for buildings of up to two storeys.